okay copy pasting with the quotes worked above, but identation was removed by this crappy forum.

After some quote syntax error, probably because of this crappy forum website, it actually works even on DSM 7.2.2-72806 Update 3.

I fixed and beautified it (hopefully copy pasting it works on this website):
#!/bin/bash

# Send a notification email via the NAS. Parameters are: TAG_EVENT VARLIST value1 value2 value3 …
# Tested on DSM 6.2.4-25556 Update 6 and DSM 7.1.1-42962 Update 2

function nas_notify() {
# TAG_EVENT names the email template to be used (see /usr/syno/synoman/webman/texts/enu/mails for the English list)
local TAG_EVENT=$1

# VARLIST is the list of variables used in the email template (without the surrounding % signs)
# Note: Some variables, eg HOSTNAME, are set by the NAS and shouldn’t be included here
local VARLIST=$2

# The values to be assigned to the variables in the above list are in $3 $4 $5 …
local NTFYJSON=””
local V VAL

# Values start at this parameter
local I=3

# This command does the notify
local NTFY_CMD=”/usr/syno/bin/synonotify”

# Create the variable/value list in almost JSON format. The NAS surrounds each variable name with % signs so we do, too
if [ “$VARLIST” != “” ]; then
for V in $VARLIST; do
eval VAL=\$$I
NTFYJSON=”${NTFYJSON},\”%${V}%\”: \”${VAL}\””
I=$((I + 1))
done

# Drop the leading comma from NTFYJSON and enclose the result in braces for actual JSON
NTFYJSON=”{${NTFYJSON:1}}”
fi
[ -x “$NTFY_CMD” ] && “$NTFY_CMD” “$TAG_EVENT” “$NTFYJSON”
}

nas_notify “ShareSyncError” “S2S_SERVER S2S_TASK DUR” “${BASH_SOURCE[0]}” “Message about the failure” “0 days 0 hours 0 mins 1 secs”

exit $?

Definition snipped from /usr/syno/synoman/webman/texts/enu/mail:

[DSMSupportFormCustomFailure]
Category: System
Level: NOTIFICATION_ERROR
Desktop: %CUSTOM_MSG%.

[DSMSupportFormCustomMessage]
Category: System
Level: NOTIFICATION_INFO
Desktop: %CUSTOM_MSG%.

Unfortunately this doesn’t seem to work with DSM 7.2

Thx a lot for sharing!

#!/bin/bash

# Send a notification email via the NAS. Parameters are: TAG_EVENT VARLIST value1 value2 value3 …
# Tested on DSM 6.2.4-25556 Update 6 and DSM 7.1.1-42962 Update 2
function nas_notify()
{
# TAG_EVENT names the email template to be used (see /usr/syno/synoman/webman/texts/enu/mails for the English list)
local TAG_EVENT=${1}
# VARLIST is the list of variables used in the email template (without the surrounding % signs)
# Note: Some variables, eg HOSTNAME, are set by the NAS and shouldn’t be included here
local VARLIST=${2}
# The values to be assigned to the variables in the above list are in $3 $4 $5 …
local NTFYJSON V VAL
# Values start at this parameter
local I=3
# This command does the notify
local NTFY_CMD=”/usr/syno/bin/synonotify”
# Create the variable/value list in almost JSON format. The NAS surrounds each variable name with % signs so we do, too
if [ “${VARLIST}” != “” ]; then
for V in ${VARLIST}; do
eval VAL=\$$I
NTFYJSON=”${NTFYJSON},’%${V}%’: ‘${VAL}'”
I=$(( I + 1 ))
done
# Drop the leading comma from NTFYJSON and enclose the result in braces for actual JSON
NTFYJSON=”{${NTFYJSON:1}}”
fi
[ -x “${NTFY_CMD}” ] && ${NTFY_CMD} “${TAG_EVENT}” “${NTFYJSON}”
}

nas_notify “ShareSyncError” “S2S_SERVER S2S_TASK DUR” “${BASH_SOURCE[0]}” “Message about the failure” “0 days 0 hours 0 mins 1 secs”

exit $?

Anyway, thanks for putting this out there! If, and when, you make the move to DSM 7.x, I do hope you’ll share any solutions you come up with. I feel absolutely lost without it. Hijacking an used notification works, to a degree, but I really miss having the Desktop notification flow displaying my custom details.

Sorry, quick correction – the additional single quotes worked in the CLI, but I had to add an extra layer of double quotes to work inside the bash script.

So my successful implementation was as follows:
/usr/syno/bin/synonotify tag_event ‘{“%VAR%”: “‘”$var”‘”}’

The additional single quotes around the variable fixed this for me, thanks!

I never tried myself…

But: as users may subscribe (or not) on events to be notified, via Control Panel > Notifications > Advanced
I would suggest that: if you want only one user to be notified, tell that one only to subscribe on your custom notifications.